Many oil and gas wells have sufficient downhole pressure to flow to the surface. Others, however, require production utilizing gas-lift methods. Gas-lift valves are installed in a string of production tubing at specified elevations in the well. Ordinarily, gas-lift valves are physically located in sidepockets on the tubing string. Sidepockets are off to the side of the main axis of the tubing string. Production is achieved by introducing gas through a gas-lift valve into the production tubing string. Sometimes, however, gas-lift valves fail and require servicing in some form or fashion. They must be removed or replaced. In wells which are slanted, there is some difficulty in locating a sidepocket because the natural path of movement of a retrieval or installation tool is centered along the axis of the tubing string but hangs toward the vertical. Moreover, an operator at the surface who is manipulating a retrieval tool on a wireline does not know the precise azimuthal location of a sidepocket, even when he does known the relative elevation. Consider an easy example. Suppose a surface operator knows that a sidepocket is located at 5,000 feet in the well. The sidepocket may be located on the north side of the well. The well at this depth may, additionally, be a slant hole, slanting by ten degrees to the east. Such precise location of the sidepocket is usually not readily known, and, even when available, it is difficult to manipulate the angular orientation of valve installation equipment on a wireline.
The present inventor previously devised a kick-over tool disclosed in U.S. Pat. No. 3,828,853. That apparatus is believed to be functioning quite nicely. It operates nicely in vertical wells, as well as those which are deviated or slant wells. It particularly causes the retrieval tool to kick over into the sidepocket. Applicant's prior structure utilizes four bow springs which are freed for expansion at the time of retrieval or installation. When the four bow springs are released, all of the springs are confined, except a bow spring which forces the lower end of the tool to deflect into the sidepocket. This apparatus, while quite successful, normally contemplates expansion of four low springs. The four bow springs cannot all expand; expansion is limited by the relief permitted to the lower end of the tool as the kick-over tool deflects into the sidepocket.
The present invention is an improvement over the prior apparatus of applicant. The prior apparatus has functioned quite nicely and continues to do so. However, this invention goes one step further in the provision of dual coil springs which initiate kick-over. The coil springs work against pairs of the bow springs to deflect them outwardly. Ordinarily, dimensions are such that only a pair of bow springs will be permitted to fully deflect. Only one pair of bow springs normally has room to expand and deflect when the sidepocket is located. Conversely, the other two bow springs, which are located at ninety degrees with respect to the first pair, are not permitted to expand or deflect. In other words, it is inevitable in practically every dimensional situation that two of the springs will deflect outwardly to the maximum permitted, while the other two springs will deflect outwardy only by a short distance. Their deflection is constrained by the limitations of space. Assume, for examle, that the tubing string is 27/8 inch nominal size. If the tool, itself, is about two inches in diameter, one pair of opposing bow springs will deflect by only about one-half inch for each of the two bow springs. The other two bow springs will deflect by two or three times, or more. This results in some variation of the length of the bow springs after deflection. The present invention utilizes two coil springs to accommodate such deflections and, particularly, variations in deflection.